Air interface capacity scheduling method

ABSTRACT

A method, and a radio transmitter using the method, is disclosed for scheduling air interface capacity between user services in a radio system. The method includes defining a nominal service bit rate, a nominal capacity of the service, and an effective coding rate of the service, and scheduling air interface frame capacity between at least two different services. The scheduling includes computing the bit rate of a first service by multiplying the nominal capacity of the first service by the effective coding rate of the first service, and adding to this normal bit rate of the first service borrowed extra capacity of at least one other service, the bit rate obtained from the extra capacity computed by multiplying a predetermined amount of the nominal capacity of the other service by the effective coding rate of the first service.

FIELD OF THE INVENTION

The invention relates to a radio system, more particularly to a methodof scheduling air interface capacity between different user services.

BACKGROUND OF THE INVENTION

One of the major problems in mobile telephone systems is limited radiocapacity. In current systems, a certain amount of radio capacity isreserved for each user having a circuit switched connection for theentire duration of a connection. In packet switched transmission, wherethe data transferred is typically generated in bursts, it is a waste ofradio capacity to keep radio capacity reserved according to the highestmomentarily needed transmission capacity. Different kinds of methodshave therefore been developed for flexible allocation of radio capacity.

A new problem is that a single user may use simultaneously severaldifferent services. A certain amount of total capacity to be used fordata transmission is then reserved for the user. The user also wants touse the capacity he is paying for as efficiently as possible.

Several such services exist simultaneously and the system has to beefficient in supporting diverse combinations of services. In thirdgeneration mobile telephone systems, a wide variety of services andservice combinations are available. As these services have variablerates and the maximum instantaneous bit rate of each service may occurrarely, it is not efficient to allocate capacity based on the worstservice bit rate combination, i.e. every service transmitting at thehighest possible bit rate. On the other hand, a sudden need for morecapacity may arise for some service, in which case the system should beable to borrow extra capacity very quickly. As a system option, a userequipment (UE) having multiple bearer services can be managed as onesingle radio link connection, where radio capacity is allocated for thewhole link. Internally, UE has the task of managing the scheduling ofmultiple bearer transmission. This should reduce the resource managementtask in the network and it also reduces scheduling delay as it is nowcarried out internally by the UE. However, if multiple bearer serviceshave different QoS (Quality of Service), e.g. different level of errorprotection by channel coding, this leads to a problem that the radioresource used to transmit one information bit of one bearer does notequal to the resource used to transmit one information bit of anotherbearer.

BRIEF DESCRIPTION OF THE INVENTION

An object of the invention is therefore to provide a method and anequipment implementing the method in such a way that the above problemscan be solved. This is achieved with the method described below, whichis a method of scheduling air interface capacity between user servicesin a radio system, comprising: defining a nominal service bit rate as abit rate before channel coding and service specific rate matching;defining a nominal capacity of the service as a bit rate after channelcoding and service specific rate matching; defining an effective codingrate of the service by dividing the nominal service bit rate by thenominal capacity of the service. The method also comprises schedulingair interface frame capacity between at least two different services:computing the bit rate of the first service by multiplying the nominalcapacity of the first service by the effective coding rate of the firstservice, and adding to this normal bit rate of the first service theborrowed extra capacity of at least one other service, and the bit rateobtained from the extra capacity is computed by multiplying apredetermined amount of the nominal capacity of the other service by theeffective coding rate of the first service.

The invention also relates to an other method of scheduling airinterface capacity between user services in a radio system, comprising:defining a nominal service bit rate as a bit rate before channel coding;defining a nominal capacity of the service as a bit rate after channelcoding; defining an effective coding rate of the service by dividing thenominal service bit rate by the nominal capacity of the service. Theother method also comprises scheduling air interface frame capacitybetween at least two different services: computing the bit rate of thefirst service by multiplying the nominal capacity of the first serviceby the effective coding rate of the first service, and adding to thisnormal bit rate of the first service the borrowed extra capacity of atleast one other service, and the bit rate obtained from the extracapacity is computed by multiplying a predetermined amount of thenominal capacity of the other service by the effective coding rate ofthe first service.

The invention also relates to a radio transmitter for transmittinginformation of at least two different user services, comprising: achannel coder in each service information branch for coding theinformation; a rate matcher connected to the output of the channel coderin each service information branch for performing service specific ratematching for the information; means for defining a nominal service bitrate as a bit rate before channel coding and service specific ratematching, means for defining a nominal capacity for the service as a bitrate after channel coding and service specific rate matching; means fordefining an effective coding rate for the service by dividing thenominal service bit rate by the nominal capacity of the service. Theradio transmitter also comprises means for scheduling air interfaceframe capacity between at least two different services, including: meansfor computing the bit rate of the first service by multiplying thenominal capacity of the first service by the effective coding rate ofthe first service, and means for adding to this normal bit rate of thefirst service the borrowed extra capacity of at least one other service,and the bit rate obtained from the extra capacity is computed bymultiplying a predetermined amount of the nominal capacity of the otherservice by the effective coding rate of the first service.

The invention also relates to an other radio transmitter fortransmitting information of at least two different user services,comprising: a channel coder in each service information branch forcoding the information; means for defining a nominal service bit rate asa bit rate before channel coding; means for defining a nominal capacityfor the service as a bit rate after channel coding; means for definingan effective coding rate for the service by dividing the nominal servicebit rate by the nominal capacity of the service. The other radiotransmitter also comprises means for scheduling air interface framecapacity between at least two different services, including: means forcomputing the bit rate of the first service by multiplying the nominalcapacity of the first service by the effective coding rate of the firstservice, and means for adding to this normal bit rate of the firstservice the borrowed extra capacity of at least one other service, andthe bit rate obtained from the extra capacity is computed by multiplyinga predetermined amount of the nominal capacity of the other service bythe effective coding rate of the first service.

The invention is based on the presentation of a simple and fastreallocation algorithm, wherein the usable bit rate for the service bitsis calculated using the nominal capacity of the service, the codingrate, and the borrowed capacity of at least one other service.

The method and system of the invention provide several advantages.Flexibility of the system is improved so that the aggregate capacityallocated for the user services can be easily scheduled dynamicallybetween services according to the need and the service priority, evenfor each air interface frame separately. The radio capacity of thesystem will therefore be more fully utilized.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following the invention will be described in greater detail inconnection with preferred embodiments and with reference to the attacheddrawings, in which

FIGS. 1A and 1B illustrate an example of a mobile telephone system;

FIG. 2A illustrates a transmitter and a receiver;

FIG. 2B illustrates spreading and modulation carried out in thetransmitter;

FIG. 3 illustrates a frame structure;

FIG. 4 illustrates a part of a spreading code tree;

FIG. 5 illustrates a mobile station

FIG. 6 is a flow diagram illustrating the method of scheduling airinterface capacity;

FIGS. 7A, 7B, 7C, 7D illustrate an example of the scheduling method;

FIG. 8 illustrates a protocol stack.

DETAILED DESCRIPTION OF THE INVENTION

The present invention can be used in different mobile telephone systems.In the following examples, the use of invention is described in theUniversal Mobile Telephone System (UMTS) using the direct-sequencewide-band code division multiple access (WCDMA), the invention notbeing, however, restricted to it. The new Japanese mobile telephonesystem as specified by the ARIB (The Association of Radio Industries andBusinesses), for example, is therefore also a mobile telephone systemaccording to the invention.

With reference to FIGS. 1A and 1B, a typical mobile telephone systemstructure will be described. FIG. 1B only comprises the blocks that areessential for the description of the invention, although it is apparentto a person skilled in the art that a common mobile telephone systemalso comprises other functions and structures which need not bediscussed in greater detail here. The main parts of the mobile telephonesystem are: a core network CN, a UMTS terrestrial radio access networkUTRAN, and a user equipment UE. The interface between the CN and theUTRAN is called the lu interface, and the interface between the UTRANand the UE is called the Uu interface.

The UTRAN is composed of radio network subsystems RNS. The interfacebetween two RNSs is called the lub interface. The RNS is composed of aradio network controller RNC and one or more node Bs B. The interfacebetween the RNC and the node B is called the lub interface. Thereception area of the node B, i.e. cell, is denoted in FIG. 1A with a C.

As the presentation in FIG. 1A is very abstract, it is clarified in FIG.1B by setting forth the parts of the GSM system that correspond with theparts of the UMTS. It is clear that the presented mapping is by no meansa binding one but an approximation, because the responsibilities andfunctions of the parts of the UMTS are still under heavy planning.

FIG. 1B illustrates a packet switched transmission via Internet 102 froma computer 100 connected with the mobile telephone system to a portablecomputer 122 connected with an user equipment UE. The user equipment UEmay be a fixedly mounted wireless local loop terminal, a vehicle-mountedterminal or a handheld portable terminal, for example.

The infrastructure of the radio network UTRAN is composed of radionetwork subsystems RNS, i.e. base station subsystems. The radio networksubsystem RNS is composed of a radio network controller RNC, i.e. a basestation controller, and at least one node B, i.e. a base station, underthe control of the RNC.

The base station B comprises a multiplexer 114, transceivers 116, and acontrol unit 118 which controls the operation of the transceivers 116and the multiplexer 114. The multiplexer 114 arranges the traffic andcontrol channels used by a plurality of transceivers 116 to a singletransmission connection lub.

The transceivers 116 of the base station B have a connection to anantenna unit 120 which is used for providing a bi-directional (orsometimes one-way) radio connection Uu to a user equipment UE. Thestructure of the frames transmitted in the radio connection Uu isdetermined in detail and the connection is referred to as an airinterface.

The base station controller RNC comprises a group switching field 110and a control unit 112. The group switching field 110 is used forswitching speech and data and for connecting signaling circuits. Thebase station B and the base station controller RNC form a base stationsubsystem which additionally comprises a transcoder, also known as aspeech codec, or TRAU (Transcoder and Rate Adapter Unit) 108.

The division of functions and the physical structures of the basestation controller RNC and the base station B may differ according tothe actual realization of the base station subsystem. Typically, thebase station B implements the radio connection. The base stationcontroller RNC typically manages the following: radio resource control,inter-cell handover control, power control, timing and synchronization,and paging of user equipment.

The transcoder 108 is usually located as close to a mobile switchingcenter 106 as possible because this allows speech to be transmittedbetween the transcoder 108 and the base station controller RNC in acellular radio network form, which saves transmission capacity.

The transcoder 108 converts different digital speech coding modes usedbetween a public switched telephone network and a cellular radionetwork, to make them compatible, for instance from the 64 kbit/s fixednetwork form to another form (such as 13 kbit/s) of the cellular radionetwork, and vice versa. Naturally, the transcoding is carried out onlyfor speech. The control unit 112 carries out call control, mobilitymanagement, collection of statistical data and signaling.

The core network CN is composed of the infrastructure belonging to themobile telephone system not being part of the UTRAN. FIG. 1B illustratestwo equipments, which are part of the core network CN, namely a mobileswitching center 106, and a gateway mobile switching center 104, whichhandles mobile telephone systems interfaces towards the outside world,in this example towards the Internet 102.

FIG. 5 illustrates an exemplary structure of the user equipment UE. Theessential parts of the user equipment UE are: an interface 504 to theantenna 502 of the user equipment UE, a transceiver 506, a control part510 of the user equipment UE, an interface 512 to the battery 514, and auser interface comprising a display 500, a keyboard 508, a microphone516 and a speaker 518.

FIG. 2A illustrates the functioning of a radio transmitter-radioreceiver pair. The radio transmitter may be located in the node B or inthe user equipment. Correspondingly the radio receiver may be located inthe user equipment or in the node B.

The upper portion of FIG. 2A illustrates the essential functionality ofthe radio transmitter. Different services placed in a physical channelare e.g. speech, data, moving video, or still video picture, and thecontrol channels of the system that are processed in the control part214 of the radio transmitter. The control part 214 is related to thecontrol of the equipment itself and to the control of the connection.FIG. 2A illustrates manipulation of the control channel and data 200.Different services call for different source encoding equipment, forexample speech calls for a speech codec. Source encoding equipment is,however, not presented for the sake of clarity in FIG. 2A.

Different channels are then channel encoded in blocks 202A and 202B. Oneform of channel coding are different block codes, of which one exampleis cyclic redundancy check, or CRC. Another typical way of performingchannel coding is convolutional coding and its different variations e.g.punctured convolutional coding and turbo coding.

Having been channel encoded, the channels are interleaved in aninterleaver 204A, 204B. The object of interleaving is to make errorcorrection easier. In interleaving, the bits are mixed with each otherin a predetermined fashion, so that a transitory fading in the radiopath does not necessarily make the transferred informationunidentifiable. Different signals are multiplexed in block 208 in orderto be sent using the same transmitter.

Then the interleaved bits are spread with a spreading code, scrambledwith a scrambling code and modulated in block 206, whose operation isdescribed in detail in FIG. 2B.

Finally the combined signal is conveyed to the radio frequency parts210, which may comprise power amplifiers and bandwidth restrictingfilters. Analog radio signal is then transmitted through an antenna 212to the radio path Uu.

The lower portion of FIG. 2A illustrates the typical functionality of aradio receiver. The radio receiver is typically a Rake receiver. Theanalog radio signal is received from the radio path Uu by an antenna234. The received signal is conveyed to radio frequency parts 232 thatcomprise a filter which blocks frequencies outside the desired frequencyband. A signal is then converted in a demodulator 228 into anintermediate frequency or directly into baseband, and in this form thesignal is sampled and quantized.

Because the signal in question is a multipath propagated signal, effortsare made to combine the signal components propagated in differentmultipaths in block 228 which comprises several Rake fingers.

In the so-called rowing Rake finger, the delays for the differentmultipath propagated signal components are searched. After the delayshave been found, different Rake fingers are allocated for receiving eachof its multipath propagated signals by correlating the received signalwith the used spreading code delayed with the found delay of thatparticular multipath. The different demodulated and despread multipathsof the same signal are then combined in order to get a stronger signal.

The received physical channel is then demultiplexed in a demultiplexer224 into data streams of different channels. The channels are thendirected each to a de-interleaver 226A, 226B, wherein the receivedphysical channel is then de-interleaved. After that physical channelsare handled in a specific channel decoder 222A, 222B, wherein thechannel coding used in the transmission is decoded. Convolutional codingis advantageously decoded with a Viterbi decoder. Each sent channel220A, 220B, can be further processed, for example by transferring thedata 220 to the computer 122 connected with the user equipment UE. Thecontrol channels of the system are conveyed to the control unit 236 ofthe radio receiver.

FIG. 2B illustrates in more detail spreading of the channel with thespreading code and the scrambling code, and modulation of the channel.In FIG. 2B from left comes the bit stream of the channel into the blockS/P, wherein serial to parallel conversion is carried out for each twobit sequences, whereby one bit is conveyed into the I branch of thesignal and the other bit is conveyed into the Q branch of the signal.Then the I and the Q branches of the signal are multiplied with the samespreading code c_(ch), whereby relatively narrow-band information isspread into a wide frequency band. Each radio connection Uu has its ownspreading code with which the receiver recognizes the transmissionsmeant for itself. Then the signal is scrambled by multiplying it withthe scrambling code c_(scramb) that is different for each user equipmentand each base station. The pulse form of the produced signal is filteredwith a filter p(t). Finally the signal is modulated into a radiofrequency carrier by multiplying the different branches with a carrier.There is a 90 degree phase shift between the carriers of the differentbranches. The branches are then combined into one carrier which is readyto be sent into the radio path, excluding possible filtrations and poweramplifications. The described modulation is QPSK (Quadrature Phase ShiftKeying).

In FIG. 4 examples of different spreading codes are illustrated. Eachdot 400 represents one possible spreading code. The vertical brokenlines represent different spreading factors (SF) SF=1, SF=2, SF=4, SF=8,SF=16, SF=32, SF=64, SF=128, SF=256. The codes being located on thevertical broken line are mutually orthogonal. Two hundred fifty-sixmutually orthogonal spreading codes can then maximally exist. Forexample in the UMTS, when a 4.096 megachip carrier is used, thespreading factor SF=256 corresponds to a transmission rate of about 32kilobits/second. Correspondingly, the highest usable transmission rateof 2048 kbit/s is achieved with the spreading code having the spreadingfactor SF=4. The transmission rate that the user obtains depends on thechannel coding used, e.g. while using ⅓ convolutional coding thetransmission rate visible to the user is about one third of the actualtransmission rate of the channel. The spreading factor may indicate thelength of the spreading code. For example the spreading code (1)corresponds with the spreading factor SF=1. On the spreading factorlevel SF=2 there are two mutually orthogonal spreading codes (1,1) and(1,0). The spreading factor level SF=4 has four mutually orthogonalspreading codes (1,1,1,1), (1,1,0,0), (1,0,1,0) and (1,0,0,1). So theformulation of the spreading codes is continued while traveling towardsthe lower levels of the code tree. The spreading codes at a certainspreading factor level are usually mutually orthogonal, e.g. inWalsh-Hadamard code sets.

FIG. 3 shows an example of a possible frame structure used in thephysical channel. Frames 340A, 340B, 340C, 340D are given a runningnumber from one to seventy-two, and they form a 720 millisecond longsuper frame. The length of one frame 340C is ten milliseconds. The frame340C is divided into sixteen slots 330A, 330B, 330C, 330D. The length ofslot 330C is 0.625 milliseconds. One slot 330C corresponds typicallywith one power control period during which power is adjusted e.g. onedecibel up or down.

The physical channels are divided into different types, including commonphysical channels and dedicated physical channels. The dedicatedphysical channels consist of dedicated physical data channels (DPDCH)310 and dedicated physical control channels (DPCCH) 312. DPDCHs 310 areused to carry data 306 generated in layer two and above of the OSI (OpenSystems Interconnection) model, i.e. dedicated control channels anddedicated traffic channels. DPCCHs 312 carry the control informationgenerated in layer one of the OSI model. Control information comprises:pilot bits 300 used in channel estimation, transmit power-controlcommands (TPC) 302, and optionally transport format indicator (TFI) 304.TFI 304 tells the receiver the transport formats of different transportchannels, i.e. Transport Format Combination, used in the current frame.Transport Format is a set of parameters, including the currenttransmission rate.

As can be seen from FIG. 3, down-link DPDCHs 310 and DPCCHs 312 are timemultiplexed into the same slot 330C. Conversely, in the up-link, thechannels are sent in parallel so that they are IQ/code multiplexed(I=in-phase, Q=quadrature) into each frame 340C and they are sent byusing dual-channel quadrature phase-shift keying modulation. Whenadditional DPDCHs 310 are to be sent, they are code multiplexed into theI or Q branch of the first channel pair.

The channels in the radio interface Uu are handled according to aprotocol architecture comprising, according to the ISO (InternationalStandardization Organization) OSI (Open Systems Interconnection) model,three protocol layers: a physical layer (=layer one), a data link layer(=layer two), and a network layer (=layer three). The other layers ofthe OSI model are not interesting from the invention's point of view.The protocol stacks are located both in the radio network subsystem RNSand in the user equipment UE. FIG. 8 illustrates the layers of theprotocol architecture. The oval circles between different sublayersindicate service access points (SAP).

The physical layer L1 offers different transport channels to the MACsub-layer MAC and higher layers. The physical layer transport servicesare described by how and with what characteristics data is transferredover the radio interface. The transport channels include Random AccessChannel (RACH), Forward Access Channel (FACH), Broadcast Channel (BCH),Paging Channel (PCH), and Dedicated Channel (DCH). The physical layer L1maps transport channels with physical channels. In the FDD (FrequencyDivision Duplex) mode a physical channel is characterized by the code,frequency and in the reverse link the relative phase (I/Q). In the TDD(Time Division Duplex) mode the physical channel is also characterizedby the time slot.

The data link layer is divided into two sub-layers: a MAC sub-layer(Medium Access Control) and a RLC sub-layer (Radio Link Control). TheMAC sub-layer L2/MAC offers different logical channels to the RLCsub-layer L2/RLC. The logical channel is characterized by the type ofinformation that is transferred. This service provides unacknowledgedtransfer between peer MAC entities. One of the functions of the MACsub-layer is to select the appropriate transport format for eachtransport channel depending on the momentary source bit rate.

The third layer L3 has a RRC sub-layer (Radio Resource Control) thathandles the control plane signaling of layer three between the userequipment and the network. One of the functions carried out by the RRCsub-layer is assignment, reconfiguration and release of radio resourcesfor the RRC connection. So the RRC sub-layer handles the assignment ofradio resources required for the RRC connection, including requirementsfrom both the control and user plane. The RRC layer may reconfigureradio resources during an established RRC connection.

Now in this invention we are interested in the mapping of the differentservices of one user to the same dedicated channel. According to theknown technique each service has at its disposal a predetermined amountof the capacity of the dedicated channel reserved for that user.

The method according to the invention for scheduling air interfacecapacity between services of a user in a radio system is presented inFIG. 6. The performance of the method begins in block 600. Basically, auser should have at least two concurrent services in order to be able toutilize this method. The term service applies here also to controlinformation e.g. RRC control information, therefore the controlinformation can also be scheduled according to the method of theinvention.

In block 602 a nominal service bit rate is defined as a bit rate Zbefore channel coding and service specific rate matching. This is theactual bit rate allocated for the service. It should be noted here thatthe service specific rate matching can be an optional feature, i.e.nominal service bit rate is defined as a bit rate before channel codingonly. Typically channel coding is convolutional coding, and servicespecific rate matching is repetition coding or puncturing.

In block 604 a nominal capacity of the service is defined as a bit rateY after channel coding and service specific rate matching. This is theneeded air interface transmission capacity for a given service. As withthe previous step also in this step the service specific rate matchingis optional, i.e. nominal capacity of the service is defined as a bitrate after channel coding.

In block 606 an effective coding rate R of the service is defined bydividing the nominal service bit rate by the nominal capacity of theservice, i.e. R=Z/Y.

The functionality of the blocks 602, 604. 606 is performed for everyservice that the user uses. The word “nominal” refers to a normalsituation, i.e. service bit rates required by a given service in anormal or standard situation. The coding rate is chosen on the basis ofthe bit error rate requirements for the service and the current radiointerface conditions. The nominal capacity required will be calculatedon the basis of the required channel coding and the service bit rate.

In an normal situation the nominal capacities of the services will beused. In practice some services do not need to transmit all the time andin some services higher than nominal service bit rates may be generatedoccasionally. This is especially true for applications that use packetswitched transmission, e.g. World Wide Web browser software. It would bea waste of resources to always allocate the needed theoretical maximumcapacity to the user. If some service is not transmitted at all, thenthe free radio resource can be used for transmitting some other service.

Priorities can also be defined between services, e.g. the first servicehas a higher priority than the other service, and consequently the firstservice can always borrow the capacity of the other service, if needed,even if the capacity of the other service is not free. In principle,capacity cannot be borrowed from a real-time speech service, but ifdiscontinuous transmission is used, the speech service can lend itscapacity on a frame basis.

If the user's total allocated capacity is at all times too scarce, thenmore total capacity should be allocated instead of using the presentedmethod.

In block 608, scheduling is carried out for an air interface frame byscheduling available capacity between at least two different services.First the capacity of the first service is computed by multiplying thenominal capacity of the first service K by the effective coding rate ofthe first service. The borrowed extra capacity of at least one otherservice is then added to said normal capacity of the first service, theextra capacity being computed by multiplying a predetermined amount ofthe nominal capacity of the other service J by the effective coding rateof the first service: $\begin{matrix}{Z_{K} = {{R_{K}Y_{K}} + {\sum\limits_{J = 1}^{N}\quad {R_{K}P_{J}Y_{J}}}}} & (1)\end{matrix}$

where P_(j)ε[0,1] is the free % of Y_(j,)

N is the number of borrowing services, and

M is the total amount of services, and N<M.

Service K can therefore lend capacity from a number of services, themaximum being M−1 other services. It can lend all capacity of someservice, or only some portion of it. In an extreme case service K lendsthe whole capacity of all other services.

The bit rate of each other service can be computed by multiplying theremaining nominal capacity of the other service by the effective codingrate of the other service:

Z _(j) =R _(j)(1−P _(j))Y _(j)  (2)

The method of the invention can be implemented, for example, in the RRCsub-layer and MAC sub-layer. The transport format indicator (it can alsobe called rate indicator or transport format combination indicator) isused to indicate the mixture of services used in the frame. Selection ofthe appropriate transport format for each transport channel depends onthe amount of data in transmission buffers. Given the transport formatcombination set, assigned by layer three e.g. RRC sub-layer, MACsub-layer selects the appropriate transport format within an assignedtransport format set for each active transport channel depending onamount of data in the transmission buffers. Control of transport formatsensures efficient use of transport channels. A transport formatcombination set refers to all combinations of transport formats ofdifferent services.

In basic case the bit rate combination of different services in the airinterface frame is signaled to the recipient by the transport formatindicator. One service can borrow the capacity of some other service aspreviously presented. The ratio between the capacities of differentservices may be freely definable but this presupposes more signaling,i.e. the multiplexing structure has to be signaled for every frame.Another way to implement the invention is to only allow predeterminedcapacity combinations of different services in the air interface frameand to reserve one TFI word for each such service combination. Then onlytransport format indicator needs to be used as the recipient has in itsmicroprocessor's memory the stored information telling which transportformat indicator value corresponds to which multiplexing structure ofthe services.

Still another way is to use a blind detection algorithm in the receiverto determine the capacity combination used in the received air interfaceframe. This can be implemented in many ways, one exemplary way is todefine a rule saying that the borrowing is possible in somepredetermined sections, e.g. in sections being 100 bit long. Thereceiver finds the right combination by utilizing the blind detectionalgorithm. This solution has the advantage that the signaling of themultiplexing structure is not necessarily needed.

Next, an elaborated example illustrating the scheduling method isexplained in connection with FIGS. 7A, 7B, 7C, 7D. Only some of thepossibilities for scheduling will be illustrated, but it will be clearfor a person skilled in the art how scheduling can be performed for adifferent number of services and with different scheduling ratios.

FIG. 7A illustrates the data 200 and the channel coding 202B of FIG. 2A.Let us assume that the user uses two services, the first service havinga nominal service bit rate Z₁ of 3000 bits, and the second servicehaving a nominal service bit rate Z₂ of 750 bits. Let us further assumee.g. that the bit error rate requirement for the first service isBER10⁻³, the used channel coding consequently being only ½ convolutionalcoding performed in a channel coder 700A, but a service specific ratematching with 1.5 repetition coding also being performed in a ratematcher 702A. The required BER of the second service is 10⁻⁶, thechannel coding consequently being heavier, i.e. the ¼ convolutionalcoding, but no service specific rate matching will be done, whereby themultiplier is one in block 702B. After the required channel coding andservice specific rate matching, the nominal transmission capacityrequired is Y₁=9000 bits for the first service and Y₂=3000 bits for thesecond service. The coding rate of the first service is R₁=Z₁/Y₁=⅓ andthe coding rate of the second service is R₂=Y₂/Z₂=¼.

The multiplexing block 704 multiplexes the coded bit streams of theservices in some specific way into one bit stream. The total capacityrequired is 12000 bits. The user can use these 12000 bits maximally atany given time. Typically one spreading code is reserved for the user,whereby the same transmission power is used for the bits of the firstand second service, but the channel coding and service specific ratematching can be different, depending on the BER requirements.

The control unit 214 controls the blocks that are connected to it with abroken arrow-headed line. The invention is preferably implemented bysoftware, but also ASIC (Application Specific Integrated Circuit) orsome other HW implementation is of course possible. The channel coder700A, 700B, the rate matcher 702A, 7028, the means 214 for defining anominal service bit rate, the means 214 for defining a nominal capacityof the service, the means 214 for defining an effective coding rate ofthe service, the means 214 for scheduling for an air interface frame thecapacity between at least two different services, the means 214 forcomputing the bit rate of the first service, the means 214 for addingthe borrowed extra capacity of the other service to this normal bit rateof the first service, and the means 214 for computing the bit rate ofthe other service can consequently be software modules of the protocolstack residing in the user equipment UE, and in the radio networksubsystem RNS.

FIG. 7A illustrates the required nominal capacities that may be used ina normal situation. In FIG. 7B the first service may use the entirenominal capacity of the second service, i.e. Z₂=0 bits, real Y₂=0 bits,and real Y₁=12000 bits. The allowed service bit rate of the firstservice can be computed: Z₁=R₁Y₁+R₁P₂Y₂=⅓(9000)+⅓(1*3000)=4000 bits.

In FIG. 7C the situation is reversed: the second service may now use theentire nominal capacity of the first service, i.e. Z₁=0 bits, real Y₁=0bits, and real Y₂=12000 bits. The allowed service bit rate of the secondservice can be computed: Z₂=R₂Y₂+R₂P₁Y₁=¼(3000)+¼(1*9000)=3000 bits.

In FIG. 7D the first service has borrowed from the second service 50% ofits capacity, i.e. the real Y₁=9000+0.5*3000=10500 bits and the realY₂=0.5*3000=1500 bits. The service bit rate of the first service isZ₁=R₁Y₁+R₁P₂Y₂=⅓(9000)+⅓(0.5*3000)=3500 bits. The service bit rate ofthe second service is Z₂=R₂(1−P₂)Y₂=¼(0.5*3000)=375 bits.

Even though the invention is described above with reference to anexample shown in the attached drawings, it is apparent that theinvention is not restricted to it, but can vary in many ways within theinventive idea disclosed in the attached claims.

What is claimed is:
 1. A method of scheduling air interface capacitybetween user services in a radio system, comprising: defining a nominalservice bit rate as a bit rate before channel coding and servicespecific rate matching; defining a nominal capacity of the service as abit rate after channel coding and service specific rate matching;defining an effective coding rate of the service by dividing the nominalservice bit rate by the nominal capacity of the service; and schedulingair interface frame capacity between at least two different userservices, including: computing the bit rate of a first service bymultiplying the nominal capacity of the first service by the effectivecoding rate of the first service, and adding to this normal bit rate ofthe first service borrowed extra capacity of at least one other service,the bit rate obtained from the extra capacity computed by multiplying apredetermined amount of the nominal capacity of the other service by theeffective coding rate of the first service.
 2. A method of schedulingair interface capacity between user services in a radio system,comprising: defining a nominal service bit rate as a bit rate beforechannel coding; defining a nominal capacity of the service as a bit rateafter channel coding; defining an effective coding rate of the serviceby dividing the nominal service bit rate by the nominal capacity of theservice; and scheduling air interface frame capacity between at leasttwo different user services, including: computing the bit rate of afirst service by multiplying the nominal capacity of the first serviceby the effective coding rate of the first service, and adding to thisnormal bit rate of the first service borrowed extra capacity of at leastone other service, the bit rate obtained from the extra capacitycomputed by multiplying a predetermined amount of the nominal capacityof the other service by the effective coding rate of the first service.3. A method according to claim 1, wherein the borrowed extra capacity isan unused part of the nominal capacity of the other service.
 4. A methodaccording to claim 1, wherein the first service has a higher prioritythan the other service.
 5. A method according to claim 1, wherein acapacity combination of different services in the air interface frame issignaled to a recipient.
 6. A method according to claim 1, whereinallowed capacity combinations of different services in the air interfaceframe are predetermined.
 7. A method according to claim 6, wherein areceiver uses a blind detection algorithm to determine the capacitycombination used in the received air interface frame.
 8. A methodaccording to claim 1, wherein the bit rate of the other service iscomputed by multiplying remaining nominal capacity of the other serviceby the effective coding rate of the other service.
 9. A radiotransmitter for transmitting information of at least two different userservices, comprising: a channel coder in each service information branchfor coding the information; a rate matcher connected to the output ofthe channel coder in each service information branch for performingservice specific rate matching for the information; means for defining anominal service bit rate as a bit rate before channel coding and servicespecific rate matching; means for defining a nominal capacity for theservice as a bit rate after channel coding and service specific ratematching; means for defining an effective coding rate for the service bydividing the nominal service bit rate by the nominal capacity of theservice; and means for scheduling air interface frame capacity betweenat least two different user services, including: means for computing thebit rate of a first service by multiplying the nominal capacity of thefirst service by the effective coding rate of the first service, andmeans for adding to this normal bit rate of the first service borrowedextra capacity of at least one other service, the bit rate obtained fromthe extra capacity computed by multiplying a predetermined amount of thenominal capacity of the other service by the effective coding rate ofthe first service.
 10. A radio transmitter for transmitting informationof at least two different user services, comprising: a channel coder ineach service information branch for coding the information; means fordefining a nominal service bit rate as a bit rate before channel coding;means for defining a nominal capacity for the service as a bit rateafter channel coding; means for defining an effective coding rate forthe service by dividing the nominal service bit rate by the nominalcapacity of the service; and means for scheduling air interface framecapacity between at least two different user services, including: meansfor computing the bit rate of a first service by multiplying the nominalcapacity of the first service by the effective coding rate of the firstservice, and means for adding to this normal bit rate of the firstservice borrowed extra capacity of at least one other service, the bitrate obtained from the extra capacity computed by multiplying apredetermined amount of the nominal capacity of the other service by theeffective coding rate of the first service.
 11. A radio transmitteraccording to claim 9, wherein the means for scheduling uses an unusedpart of the nominal capacity of the other service as the borrowed extracapacity.
 12. A radio transmitter according to claim 9, wherein themeans for scheduling recognizes that the first service has a higherpriority than the other service.
 13. A radio transmitter according toclaim 9, further comprising means for signaling a capacity combinationof different services in the air interface frame to a recipient.
 14. Aradio transmitter according to claim 9, further comprising means forstoring predetermined allowed air interface frame capacity servicecombinations.
 15. A radio transmitter according to claim 14, furthercomprising a blind detection algorithm to determine which capacitycombination was used in the received air interface frame.
 16. A radiotransmitter according to claim 9, further comprising means for computingthe bit rate of the other service by multiplying remaining nominalcapacity of the other service by the effective coding rate of the otherservice.
 17. A method according to claim 2, wherein the borrowed extracapacity is an unused part of the nominal capacity of the other service.18. A method according to claim 2, wherein the first service has ahigher priority than the other service.
 19. A method according to claim2, wherein a capacity combination of different services in the airinterface frame is signaled to a recipient.
 20. A method according toclaim 2, wherein allowed capacity combinations of different services inthe air interface frame are predetermined.
 21. A method according toclaim 20, wherein a receiver uses a blind detection algorithm todetermine the capacity combination used in the received air interfaceframe.
 22. A method according to claim 2, wherein the bit rate of theother service is computed by multiplying remaining nominal capacity ofthe other service by the effective coding rate of the other service. 23.A radio transmitter according to claim 10, wherein the means forscheduling uses an unused part of the nominal capacity of the otherservice as the borrowed extra capacity.
 24. A radio transmitteraccording to claim 10, wherein the means for scheduling recognizes thatthe first service has a higher priority than the other service.
 25. Aradio transmitter according to claim 10, further comprising means forsignaling a capacity combination of different services in the airinterface frame to a recipient.
 26. A radio transmitter according toclaim 10, further comprising means for storing predetermined allowed airinterface frame capacity service combinations.
 27. A radio transmitteraccording to claim 26, further comprising a blind detection algorithm todetermine which capacity combination was used in the received airinterface frame.
 28. A radio transmitter according to claim 10, furthercomprising means for computing the bit rate of the other service bymultiplying remaining nominal capacity of the other service by theeffective coding rate of the other service.